The protection of the environment is now a matter of great concern. Also, the recovery and reuse of industrial resources has become a matter of vital economic interest for many industries. As a result, the disposal or reuse of industrial effluent, machine tool coolant, oily water mixtures, and industrial organic wastes has become important to many industries in the United States and internationally.
More specifically, the contamination of water and other fluids by grease, fuel, oil, and other contaminants poses a significant environmental and economic problem in the United States and elsewhere. Across the United States, there are innumerable establishments such as car and truck washes motor vehicle service stations, motor vehicle and machine repair shops, construction equipment cleaning shops, machine tool cleaning shops, meat rendering plants, restaurants, and many other types of establishments that generate contaminated water as a result of their cleaning processes. Also, rainwater runoff from highways and parking lots, crude oil tank farms, petrochemical facilities, and clean up on off-shore oil platforms are additional sources of contaminated water.
Further still, it is known that many substantially depleted oil wells contain significant quantities of oil mixed in with ground water. Presently, some of the useful oil is separated from the ground water by use of retention ponds and skimming the oil, but some of the oil remains in the water, often in emulsified form. The water generally cannot be released into the surface environment because of such residual oil content, and is pumped back into the well or kept in the retention ponds for long periods of time. If more efficient methods were available for separating the oil from the water, the water could more quickly and readily be discharged into the environment, for example to replenish wetlands often found in coastal oil producing areas.
The contamination of ground water, water supplies, sewage systems, and street drainage systems due to the discharge of such contaminated waters is a concern of the United States Environmental Protection Agency, and state and local environmental agencies. Therefore, the removal of immiscible and emulsified components, and other contaminants which are mixed with water, is preferable for the safe and legal disposal or reuse of such contaminated water.
A variety of methods and apparatus are known in the art for separating immiscible components and removing other contaminants from fluids. For example, one apparatus which is used for separating immiscible oily components mixed in a fluid is the Quantek CPS fluid treatment apparatus. This apparatus utilizes a coalescer plate system, and is manufactured by Quantek, Inc., of Tulsa, Okla. The Quantek apparatus is used for the treatment of oil-contaminated waste water, and it comprises the system of passing water through a stack of closely spaced, corrugated, polypropylene plates, after which the water flows past an oil dam, and exits the apparatus.
Although the Quantek apparatus can reduce the level of immiscible oil in water, it has many drawbacks. First, and most importantly, the apparatus is not effective in breaking up emulsions. Second, the level of fluid purity that may be achieved by this apparatus is limited. The range of contaminants that may be removed by the Quantek apparatus is limited to those components which are removed solely by gravimetric separation and oleophilic attraction in the coalescer. The apparatus does not remove other water soluble organic contaminants as effectively as is desired, or reduce the turbidity of the water. Finally, the Quantek apparatus is costly to maintain as it must be shut down periodically for the removal of accumulated contaminants within the system.
An example of a waste fluid treatment apparatus that is capable of breaking up emulsions is the liquid separating and recycling apparatus described in U.S. Pat. No. 4,361,488. This liquid separating and recycling apparatus removes solid contaminants from tramp oil which contains aqueous emulsions. Once the emulsions are separated, the remaining aqueous liquid is continually recirculated through the treatment loop which contains a filter followed by a coalescer. The filter removes dirt, grit, and other solid contaminants from the oil-contaminated water before the water enters the coalescer. The coalescer comprises one or more fibrous filter bed coalescer units which preferably are upright spools wound with strands of yam or synthetic fiber.
Although the liquid separating and recycling apparatus is capable of breaking up emulsions, this system is limited in that it is more costly to maintain. First, it must be shut down periodically for the removal of accumulated contaminants within the system. Further, the filter being positioned prior to the coalescer in the recirculating treatment loop greatly reduces the useful life of the filter as higher levels of contaminants enter the filter. Therefore, the system must also be shut down for the cleaning or replacement of the filter.
An example of a more recent innovative water treatment system is a water bioremediation apparatus which is manufactured by Biotek Environmental Services, Inc. of Houston, Tex., under the mark "Waste Buster." The Biotek apparatus is used for continuous or batch treatment of oily waste water. The Biotek system comprises a large treatment tank, a means for introducing oil metabolizing microorganisms and catalysts, a vertically-flowing honeycomb configured oleophilic coalescer, pumps for recirculating the waste/microorganism mixture through the coalescer, and an output filter. The Biotek system is less expensive to maintain as the microorganisms metabolize oil and other contaminants within the apparatus, thus reducing the rate of accumulation of contaminants within the apparatus. Since the microorganisms effectively "clean" certain contaminants from the system, the frequency of shut-downs for the removal of the accumulated contaminants is reduced.
Although the Biotek apparatus is less costly to maintain, the level of fluid purity that may be achieved by this apparatus is limited. The range of contaminants that are removed by the Biotek apparatus is limited in that it employs only one filter. Because of its lack of an absorption filter it cannot handle most organic chemical emulsions. The coalescer used in the Biotek apparatus, which is a vertical flow type coalescer, is limited in flow capacity and efficiency. The degree and efficiency of aeration is also limiting factor in the speed of the biodegradation. Further, the Biotek apparatus is limited in that generally the fluid must be treated in a batch process mode unless the fluid is not highly contaminated. Therefore, the method of treatment used in the Biotek apparatus is directed by the level of contamination of the fluid, and not by the user's fluid supply volume needs.
An example of an oil decontamination and water recycling system that is operable in a continuous mode for the treatment of highly contaminated water is the single pass treatment system described in U.S. Pat. No. 5,011,609. In this single pass treatment system, the fluid flows through several different coalescer compartments that are sequentially positioned, and then the fluid flows through an oil filter, a coalescing centrifugal separator, and a water polish filter.
Although this single pass treatment system may be used to treat a continuous supply of highly contaminated water, this single pass treatment system is limited in that it also is cumbersome and costly to produce, operate, and maintain. This system is more costly and cumbersome as it employs several different types of coalescers and filters, some of which may require frequent cleaning or replacement. Further, the single pass treatment system is limited in that it is operable only in a continuous treatment mode. Therefore, the single pass treatment system cannot be utilized by industries which require batch fluid treatment because of the source of their contaminated fluid.
Although there are a variety of systems known in the art for removing immiscible components and other contaminants from fluids, as demonstrated above, these known systems all have limitations and drawbacks, and therefore they do not meet the current environmental or economic needs of various industries. Therefore, what is needed is a high efficiency waste fluid treatment system for the treatment of waste fluids that contain emulsions. Further, this system needs to be rapid, easy and inexpensive to operate and maintain, flexible in order to meet a user's changing needs for either batch or continuous fluid treatment, and easy to switch between its batch and continuous fluid treatment modes. Moreover, it is believed that a treatment process involving multiple passes through a coalester may enhance gravimetric separation and efficiency and extends the useful life of filters and absorbers (such as activated carbon), thereby reducing maintenance and replacement costs.